<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<script src="tools.js" type="text/javascript"></script>
<script>
    //    alert("你好！");
    //    var a = 1;
    //    var b = 2;
    //    console.log("a = " + a + "," + "b = " + b);
    //    var c = 0;
    //    c = b;
    //    b = a;
    //    a = c;
    //    console.log("a = " + a + "," + "b = " + b);

    var a = 1;
    var b = 2;
    var sum = a + b;
    a = sum - a;
    b = sum - b;
    console.log("a = " + a + "," + "b = " + b);


</script>
</body>
</html>